In a wireless network, a wireless device may communicate with one or more radio network nodes to transmit and receive voice traffic, data traffic, control signals, and so on. FIG. 1 is a block diagram illustrating an example of a wireless network 100 that includes wireless devices 200 (which may interchangeably be referred to as user equipment, UEs) and network nodes 101 (which may interchangeably be referred to as enhanced node Bs, eNBs, or base stations). Each network node 101 may have an associated coverage area 120. For example, when wireless device 200b is within coverage area 120a associated with network node 101a, wireless device 200b may communicate with network node 101a to transmit or receive signal 115a. Network node 101a may be a serving cell or another cell of interest to wireless device 200b, and signal 115a may include voice traffic, data traffic, control signals, or any other suitable information communicated between a wireless device 200 and a network node 101.
Multi-Carrier or Carrier Aggregation
Certain wireless devices 200 may be able to receive data, transmit data, and/or otherwise operate with more than one serving cell. Such operation may be interchangeably referred to as multicarrier operation, carrier aggregation (CA) operation, multi-carrier system, multi-cell operation, multi-carrier operation, multi-carrier transmission, and/or multi-carrier reception. Carrier aggregation may be used for transmission of signaling and data in the uplink and downlink directions.
An individual carrier in a multi-carrier system may be referred to as a component carrier (CC). Examples of CCs include the primary component carrier (PCC), which may also be referred to as a primary carrier or anchor carrier, and the remaining one or more CCs, which may be referred to as secondary component carrier(s) (SCC(s)), secondary carrier(s), or supplementary carrier(s). The cell associated with the PCC may be interchangeably referred to as a serving cell, primary cell (PCell), or a primary serving cell (PSC). The cell associated with the SCC may be interchangeably referred to as a secondary cell (SCell) or a secondary serving cell (SSC). The PCC may carry wireless device-specific signaling. A PCC/PCell may exist in both the uplink and downlink directions in CA. In scenarios with a single UL CC, a PCell may be on the single UL CC. The network may assign different primary carriers to different wireless devices operating in the same sector or cell.
Multi-Carrier SCell Setup or Release Procedure
A multi-carrier SCell setup may refer to a procedure that enables a network node to at least temporarily setup or release the use of an SCell, in downlink (DL) and/or uplink (UL), by the CA capable wireless device 200. The SCell setup or release procedure or command may perform any one or more of: configuration of SCell(s) (i.e., SCell addition); activation of SCell(s); de-activation of SCell(s); and de-configuration of SCell(s) (i.e., SCell release);
Wireless Device Radio Measurements
Wireless device 200b may perform radio measurements with respect to network node 101a/signal 115a and/or network node 101c/signal 115c to support different functions such as mobility (e.g., cell selection, handover, etc.), positioning a wireless device, link adaption, scheduling, load balancing, admission control, interference management, interference mitigation, etc. The measurements may be performed on a serving cell as well as on neighbor cells over some known reference symbols or pilot sequences, such as primary synchronization signal (PSS), secondary synchronization signal (SSS), cell specific reference signal (CRS), channel state information-reference signal (CSI-RS), positioning reference signal (PRS), etc. In multi-carrier/CA, wireless device 200 may perform the cell measurements on the PCC as well as on one or more SCCs. Examples of measurements that a wireless device 200 may perform include cell identification, reference symbol received power (RSRP), reference symbol received quality (RSRQ), observed time difference of arrival (OTDOA), reference signals time difference (RSTD) on PRS signals, signal-to-noise ratio (SNR), signal-to-interference-plus-noise ratio (SINR), received interference power (RIP), block error rate (BLER), propagation delay between another wireless device and itself, transmit carrier power, transmit power of specific signals (e.g., transmit power of reference signals), positioning measurements, etc.
Serving Cell Interruption Due to Wireless Device Radio Measurements
Wireless device 200 may perform measurements on a deactivated SCell or other cells on the SCC with a deactivated SCell. Measurements may be performed in measurement cycles configured at wireless device 200 by higher layers. Examples of a measurement cycle may include a PRS configuration for RSTD and/or a SCell measurement cycle configured for mobility measurements (e.g., RSRP and RSRQ, respectively). SCell measurement cycles (measCycleSCell) may have periodicity of 160 ms, 320 ms, 640 ms, 1024 ms, or any other suitable period.
Wireless device 200 may retune its receiver when measuring on an SCC with deactivated SCell(s), and/or one or more neighbor cells of that SCC, without gaps. When wireless device 200 retunes its receiver before a measurement sample (such as when the bandwidth is extended to include the SCC, e.g., from 20 MHz to 40 MHz) and when wireless device 200 retunes its receiver after the measurement sample (such as when the bandwidth is reverted back to the serving carriers, e.g., from 40 MHz to 20 MHz), interruption in DL and/or UL of a serving cell occurs. The interruption may also occur when serving carrier and SCC are on the same chip. The interruption in each direction may be between 2-5 ms since wireless device 200 has to retune the center frequency and the bandwidth of the downlink. Wireless device 200 may regularly interrupt DL and/or UL of the serving cell to measure on cells of SCC with deactivated SCell(s), for example, according to the SCell measurement cycle configured by network node 101 (e.g., the eNB). Unfortunately, such interruption in DL and/or UL of a serving cell may cause serving cell performance degradation.